<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>边框圆角</title>
  <style>
    div{
      width: 400px;
      height: 400px;
      border: 1px solid black;
      margin: 0 auto;
      /* border-radius: 10px; */
      /* border-radius: 30%; */
      /* border-top-left-radius: 20px; */
      /* 椭圆 */
      border-top-left-radius: 50px 80px;   
    }


  </style>
</head>
<body>
  <div ></div>
  
</body>
</html>